Researchers say this discovery is unique because the planet, called Kepler-186f resides in a temperate region around its host star where water could exist and could possibly sustain life. Earth-sized planets are very difficult to detect because of contrast with their host stars.

While the Kepler space telescope made the initial discovery, researchers say both ground based telescopes, the W.M. Keck and Gemini observatories were critical in confirming the earth-sized planet. Its host, Kepler-186, is an m1-type dwarf star relatively close to our solar system in the milky way galaxy.

Five small planets have been found orbiting this star, four are in very short-period orbits and too hot for liquid water. The fifth is the earth-sized planet. Utilizing the Gemini north telescope, researchers were able to probe into the star system. The visiting differential speckle survey instrument on the telescope produced images with extreme detail.

Researchers say the observations from Keck and Gemini on Mauna Kea in Hawaii, combined with other data, calculations and analysis, allowed the team to be 99.8 percent confident that Kepler-186f is real.